Mathematics - 2012-12-20 (page 3 of 3)

Chris's sister

10:00 AM

@JasperLoy: no, not at all. However, I look more beautiful now. :D

user19161

@Chris'ssister But how did your gravatar change if the email is the same?

Chris's sister

@JasperLoy: I have no idea. :-)

user19161

@Chris'ssister Very mysterious, like my life.

Chris's sister

hehe.

@JasperLoy: in fact, everything is a big mistery. (imho)

user19161

@Chris'ssister Yes. Such as whether you are Chris or his sister.

Chris's sister

10:05 AM

@JasperLoy: sister is here and smiles at you :D

user19161

@Chris'ssister Yes, I was only joking, as always.

Chris's sister

:D

@JasperLoy: did you prepare for the end of the world? :)

user19161

WTF? Someone corrected another person's English to make it better, but he actually made it much worse...

user19161

I will have to do the edit myself then...

user19161

@Chris'ssister Well, it is quite a good thing for me actually if the world ends this year.

Chris's sister

10:14 AM

@JasperLoy: a different opinion here. I'm still in love with calculus and want to attend more problems and learn new things :-)

user19161

@Chris'ssister You should watch the movie "Knowing" starring Nicolas Cage. It is about the end of the world.

user19161

@Chris'ssister Good for you.

Dumb Cow

@JasperLoy It's a great movie :)

Chris's sister

@JasperLoy: I think I watched it some time ago. Yes, it's an interesting movie.

Nur

The only thing interesting about Knowing was the ending! :p

Chris's sister

10:26 AM

@JasperLoy: are you an English language teacher? You always have to say something about English language.:-) All I know about English language I learned on my own and never had a teacher for that. But honestly I enjoy learning things on my own. I particularly like to do some practice on the texts of the calculus books. :D

@JasperLoy: I like when you correct me because I learn some new things. The last thing I learned form you is that the correct way is "to refer to" and not "to refer at". :D

Old John

@JonasTeuwen So they have decided you are "competent"?

@BenjaLim Great!

Jayesh Badwaik

@JonasTeuwen Congratulations!!

BenjaLim

10:46 AM

@JonasTeuwen Are you coming to ANU?

@OldJohn I also solved problem 20 :D

Old John

@BenjaLim only another 20 to go? :)

BenjaLim

@OldJohn no problem 20 in page 87

Old John

@BenjaLim Ah OK! How many more problems to solve?

BenjaLim

like 25 or so

@OldJohn but I'm pretty sure I've done more than 15

I've done close to 20

because to solve certain problems you have to do others first.

Old John

@BenjaLim Great - when do you to have them finished by?

BenjaLim

10:55 AM

Like 18th feb? @OldJohn

Old John

Loads of time!!

BenjaLim

@OldJohn I think for me now

A career in maths

either representation theory or number theory @OldJohn

@OldJohn When I solved problem 20

Old John

@BenjaLim That would be great :)

BenjaLim

I wrote down all the maps and drew a diagram

Just had to work out every last detail to my own satisfaction.

@OldJohn I should tell you

When I did AT last semester

Old John

@BenjaLim I always wanted to do number theory - but in the end chose analysis because of suitability of supervisor :)

BenjaLim

10:56 AM

Stuff wasn't always very satisfying due to the fact that I didn't always know exactly why something was true.

@OldJohn Well then start now! That's an order!

Old John

@BenjaLim I have started - in my own slow and rather disorganised way

BenjaLim

@OldJohn I studied CA before so stuff about primes lying over; I knew the bigger picture

@OldJohn discuss with me!

Old John

I just do bits as and when I feel interested

@BenjaLim that would be good - but you are getting too far ahead of my slow progress

BenjaLim

@OldJohn well the stuff that you've covered

no matter how far "ahead" I am.

I can always discuss with you

Old John

I now have a small stack of NT books that I want to read

@BenjaLim Thanks!

BenjaLim

10:59 AM

@OldJohn OoO

@OldJohn I bought Neukirch :D

Pretty expensive though

Old John

That's expensive!

BenjaLim

But I now have this view that if I'm going to become a real mathematician, these books are going to carry me far into the future and so in the long run will be really worth the money.

Old John

I also have one NT book I bought and don't ever expect to read ...

BenjaLim

@OldJohn cassels and frolich?

Old John

Weil - Basic Number Theory!

have to go - back later!

BenjaLim

11:00 AM

ok

user19161

11:37 AM

The SE Christmas hats look silly, not the ones robjohn made.

Jonas Teuwen

@OldJohn Yes.

@BenjaLim Yes.

skullpatrol

@JonasTeuwen Hi, how are you?

Hi @HenningMakholm Merry Christmas.

Block Rockin' Beats

skullpatrol

12:12 PM

Nobody wants to be defeated...

Mats Granvik

1:20 PM

A snowball from me to you all! We have lots of snow here. I got my chosen books today. Maybe I will now understand the Z-transform.

skullpatrol

Using the curve $y^2 +2x= 13$, find the value of k for which the line $2y+x=k$ is a tangent to the curve.

user19161

2:01 PM

@skullpatrol I answered your question. Please upvote and accept!

skullpatrol

@JasperLoy Thank you, done.

N3buchadnezzar

The world is ending tommorow

user19161

@N3buchadnezzar Good.

N3buchadnezzar

Better drink up everything then, before its too late.

Mats Granvik

2:59 PM

My head hurts!
The Z-transform:
$\text{ZTransform}[n ,n,z]$
gives:
$\frac{z}{(-1+z)^2}$
But:
$\text{LaplaceTransform}[n ,n,z]$
gives:
$\frac{1}{z^2}$

Mats Granvik

3:16 PM

I think I got it:
$\text{Sum}[k*z{}^{\wedge}(-k),\{k,0,\text{Infinity}\}]$
gives:
$\frac{z}{(-1+z)^2}$
But what is it good for? Looks like just another power series to me.

Mats Granvik

3:34 PM

$\mathcal{Z}_n\left[\left(\cos \left(\frac{1}{2} (1-1) 2 \pi n\right)+\cos \left(\frac{1}{2} (2-1) 2 \pi n\right)\right) \left(\cos \left(\frac{1}{3} (1-1) 2 \pi n\right)+\cos \left(\frac{1}{3} (2-1) 2 \pi n\right)+\cos \left(\frac{1}{3} (3-1) 2 \pi n\right)\right)\right](z)$

$\frac{6 z^6}{z^6-1}$

$z=N[\Im(\rho _1),30];$

$\frac{6 z^6}{z^6-1}$
gives:
$6.0000007523624258990879694670$

Close to six but otherwise nothing special,

No wait, I did it wrong. Forgot to subtract expressions with one.

$\text{Clear}[n,z]$

$\mathcal{Z}_n\left[\cos \left(\frac{1}{2} (2-1) 2 \pi n\right) \left(\cos \left(\frac{1}{3} (2-1) 2 \pi n\right)+\cos \left(\frac{1}{3} (3-1) 2 \pi n\right)\right)\right](z)$
is equal to:
$\frac{z (2 z-1)}{z^2-z+1}$

Taking the limit:
$\lim_{z\to \infty } \, \frac{z (2 z-1)}{z^2-z+1}$
is equal to
$2$

Dumb Cow

3:53 PM

@MarianoSuárez-Alvarez Hi :)

Mats Granvik

$\text{Clear}[n,z]$

$\mathcal{Z}_n\left[\cos \left(\frac{1}{2} (2-1) 2 \pi n\right) \left(\cos \left(\frac{1}{5} (2-1) 2 \pi n\right)+\cos \left(\frac{1}{5} (3-1) 2 \pi n\right)+\cos \left(\frac{1}{5} (4-1) 2 \pi n\right)+\cos \left(\frac{1}{5} (5-1) 2 \pi n\right)\right)\right](z)$

$\frac{z \left(4 z^3-3 z^2+2 z-1\right)}{z^4-z^3+z^2-z+1}$

$\lim_{z\to \infty } \, \frac{z \left(4 z^3-3 z^2+2 z-1\right)}{z^4-z^3+z^2-z+1}$
is equal to:
$4$

skullpatrol

4:45 PM

@OldJohn Would you call this low hanging fruit?

Old John

@skullpatrol definitely

I prefer the solutions which do not use calculus

skullpatrol

@OldJohn Why is that?

Old John

I think it is a useful technique to know

I also have no idea what this question is asking

skullpatrol

@OldJohn definitely not low hanging :)

Old John

@skullpatrol I can't even visualise what the OP actually means by it

skullpatrol

4:55 PM

@OldJohn I agree, the OP should include a diagram.

Old John

@skullpatrol and explain what on earth is meant by "with 2 repeated geodesics and 1 repeated angle" - doesn't make sense to me

skullpatrol

@OldJohn I think it means the opposite sides of the "kite-like shape" are along geodesics and 2 of the interior angles are the same.

Old John

@skullpatrol possibly - but I am not sure, and not sure there is enough information to provide an answer - even if that is correct

skullpatrol

@OldJohn You could always ask for clarification in the comments, no?

Ed Gorcenski

When one creates a 4-D matrix in MATLAB, one seriously needs to consider one's coding skills and/or sanity. When these are verified to be nominal, one needs a beer.

Old John

5:07 PM

@skullpatrol Yep - done that

@EdGorcenski Good idea :)

Ed Gorcenski

5:18 PM

Anyone else get serial upvotes and then a reversal yesterday?

skullpatrol

Old John

@EdGorcenski nope - have you been annoyiing someone? :)

Gustavo Bandeira

@MatsGranvik Cheater!

Ed Gorcenski

Perhaps. My sanctions thread in meta has opened a very small can of worms.

Old John

@EdGorcenski Ooh - must go look ...

robjohn

5:27 PM

Ed Gorcenski

Very small can. Mostly people accusing me of shielding jingoism behind false generality, and me pointing out that no, in fact this is an international issue, whether we like it or not.

Will Jagy

@OldJohn, my friend Marty the gastroenterolgist is very impressed with a nutrition book called The China Study, en.wikipedia.org/wiki/The_China_Study_%28book%29 I told him you went one better, paleolithic, and eat just rocks and twigs.

robjohn

@WillJagy They're good for sharpening the teeth

Jayesh Badwaik

IMHO, the issue is
1. unsolvable (how to determine the country? IP address - TOR)
2. unimplementable (how to determine what is military technology and what is not)?
3. not really that relevant in that loss > gain.

So, even if it is a legal issue, I am not sure, how you can solve it. It likes what color are your bits?

What color are your bits?

skullpatrol

@robjohn That is quite a jump on Friday, I hope you have air conditioning ;)

Old John

5:31 PM

@WillJagy Not just those - I add a few seeds, leaves, grub, insects, ... :)

robjohn

@skullpatrol Yeah, I think that L.L.Bean has a line of Apocalypse-wear.

Will Jagy

@robjohn, yes, of course, but i keep specially shaped files for that, sometimes more than one for teeth far in the back. I do not, however, eat the files.

robjohn

@WillJagy hey, iron is good for the blood...

Ed Gorcenski

@JayeshBadwaik The issue is unsolvable, but when someone, in their profile, links their home country, and it is a country against whom you have tech transfer sanctions, then it becomes a little more dicey. I would assume if someone is intentionally "hiding", then the liability is reduced. But if someone announces "OH HEY I'M FROM IRAN" then one cannot reasonably say that they didn't know.

robjohn

@WillJagy But it wouldn't be paleolithic.

skullpatrol

5:33 PM

Ed Gorcenski

And in either case, it's hard to say what technology would be prohibited, which is why the language is so vague. If someone asked for re-entry guidance algorithms for missiles, that's a pretty big red flag.

But if someone is looking for fixes to MATLAB code for adaptive speed controller, well, that code might be used to make hula hoops, or it might be used in uranium enrichment centrifuges.

robjohn

@skullpatrol I never thought of that. I paid too much for that yogurt!

Jayesh Badwaik

@EdGorcenski exactly

Ed Gorcenski

Personally, my approach is to simply not answer those questions, thereby recusing myself of any visits from men in dark suits.

Jayesh Badwaik

But who will ask for it? ;-) And I am sure, even if does ask for it, the problem would be at the least transformed and at the most break it down into small multiple parts, use multiple accounts to ask about them and hence, prevent detection.

Also, I am sure, to really ask such questions, people have much more sophisticated methods than a hobby site. (Though that is not a defence of doing nothing.)

Ed Gorcenski

5:36 PM

Nevertheless, I would hate to find out "Iran restarts uranium enrichment after obtaining code from a well-intentioned user on SE"

Jayesh Badwaik

@EdGorcenski If it was that easy, then I am sure, almost every country would have had its own nuclear bomb by now. ;-)

Ed Gorcenski

@JayeshBadwaik You would be shocked at the level of sophistication that lacks in some industrial applications.

Jayesh Badwaik

@EdGorcenski naah, not in the least, I know what you are talking about. :-)

Ed Gorcenski

After all, the Stuxnet virus didn't go after the PCs used to design the bombs. It went after the machines that do some of the more mundane processing.

Will Jagy

@OldJohn, got my results yesterday. All lipids perfect, the only sour note is a hemoglobin A1c of 6.0, which they want from 4.8-5.6. Once before, December 2010 I had 5.9, otherwise acceptable, in eight other tests. So I think there is just some variation over time. I keep a Latex list with 7 or eight columns over time, cholesterol, sugar and so on. Persuasive of improvement over time.

skullpatrol

5:38 PM

For all those people who think the world will end on Dec. 21, please drop off your valuables at my house on Dec 20.

Jayesh Badwaik

@EdGorcenski So, if I ask you a question about a new method of analysis of diffusion process, you would refuse to answer my question?

Old John

@WillJagy Good idea - I think you also suggested that we ought to have the chance to throw out any single outlier in situations like this. Sounds good to me :)

Ed Gorcenski

No; only if you asked me to fix/provide you with the MATLAB code that can be run copy-pasta.

Jayesh Badwaik

but again, think like this:
1. the person knows there is an error in a specific line (he posts only that line on stackoverflow) (impossible to detect)
2. he has convergence issues in which case he is using a certain numerical method, so, he will ask question only about that subroutine (and that subroutine can be simple as a SVD or a Choelsky), and hence impossible to detect.

Ed Gorcenski

In that case, there should be no problem.

Old John

5:43 PM

Alternatively - become a specialist in some branch of maths which has absolutely no value to anyone outside of maths ... for example, I think Mochizuki is pretty safe

Ed Gorcenski

The only real concern is when it involves an algorithm of uncommon sophistication or specificity; something not likely to be very generalized.

There are lots of specific controls algorithms, for instance, that appeal to a very narrow audience.

Jayesh Badwaik

yup, but that audience is still across a wide spectrum, the diffusion control mechanism is as important to silicon processing as to nuclear power plant.

similarly the centrifuge thing

Jonas Teuwen

@JayeshBadwaik I stopped being the green one now.

Jayesh Badwaik

@JonasTeuwen eh... hmmm...

Jonas Teuwen

Yes.

Hah.

Will Jagy

5:46 PM

@OldJohn, emailed you the one page summary. I like to think of these as changing over time, including some degree of experimental error. Marty liked the chronological report, I think most doctors view tests as a one-time thing, where we would call each column a time series.

Jonas Teuwen

Now, I'm going for infinite-dimensional harmonic analysis.

Jayesh Badwaik

@JonasTeuwen o.O

Old John

@WillJagy Got it, thanks. I am sure the changes over time ought to be of interest to the medics - but then they would have learn more maths to analyse them ...

Jonas Teuwen

@JayeshBadwaik ?

Jayesh Badwaik

@JonasTeuwen I'm an unable to visualize it.

Jonas Teuwen

5:48 PM

Try harder.

2

Peter Tamaroff

@JonasTeuwen Now that's the spirit, goddamn!

Old John

@WillJagy Must go and hunt or gather some food - back later :)

@OldJohn, bye then.

later

Later all

6:02 PM

I am unsatisfied seeing @GustavoBandeira without hat.

Gustavo Bandeira

@JonasTeuwen My pics is a paiting, how would a hat fit there?

Jonas Teuwen

Does. Not. Matter.

It needs a bloody hat.

Potato

6:37 PM

@JonasTeuwen Are you still around?

Jonas Teuwen

My advisor is such a stereotypical mathematician. He told me he worked on a problem for ten years (made him professor) and then suddenly it occurred to him it was completely trivial and felt quite ":S" about that.

@Potato Yes.

Jayesh Badwaik

6:55 PM

@JonasTeuwen :P

Gustavo Bandeira

@JonasTeuwen I'll take a picture today.

With a hat. =D

Jonas Teuwen

You better.

Gustavo Bandeira

Haha

robjohn

Just upgraded my 10baseT hub to a Gigabit switch.

Gustavo Bandeira

►

I guess the secret is to suicide when it's raining.

skullpatrol

7:07 PM

Duh, carry an umbrella.

Jonas Teuwen

@robjohn Does it help in posting faster? 8-))).

robjohn

@JonasTeuwen Probably not. MSE is pretty low bandwidth

Jayesh Badwaik

@robjohn but surely the bandwidth must be regulated by your internet connection?

Gustavo Bandeira

7:23 PM

►

For the end of the world.

Jonas Teuwen

@robjohn Yes. So what for!

robjohn

@JayeshBadwaik It is, but the 10baseT hub was not as fast as our service is supposed to be

Old John

Anyone from Australia / New Zealand here? (or has the apocalypse started already?)

Nope - no answer - it must have started :)

robjohn

@OldJohn It is probably scheduled on Central America Time

Mayan Time Zone

Old John

@robjohn OK - will wait a bit longer

Jonas Teuwen

7:37 PM

I'm pretty much waiting for it as my leg is killing me!

My advisors stated that there are like two PhD thesis brewing in my head, but I just have to write them down 8-( 8-).

They even went as far to ask for my scrap notes to write it themselves.

Jayesh Badwaik

@robjohn ahh..

Old John

@JonasTeuwen which one?

Jonas Teuwen

Physics advisor :-).

The mathematics one stated it would be much better if only my name was on the mathematics papers.

Old John

@JonasTeuwen He wants you to get all the glory? - or he doesn't his name associated with them? :P

Jonas Teuwen

The first.

Old John

7:42 PM

That's OK then

Jonas Teuwen

He doesn't need to build his reputation anymore :-).

Old John

but the physics guy does?

Jonas Teuwen

He wants to use the result.

Old John

and he can't wait for you to publish it? ... or can't he give a reference " in a paper to appear ..."

Jonas Teuwen

8:02 PM

Indeed.

No, I have been scooped twice because I didn't publish it and someone else did it :-).

Old John

@JonasTeuwen Better to keep it to yourself and publish as soon as possible, then

Jonas Teuwen

If others can find it, doesn't it mean I was right and it was easy after all? 8-).

Old John

not necessarily

Jonas Teuwen

When not.

skullpatrol

If it turns out to be wrong that will save you the embarrassment.

Old John

8:11 PM

for example, some quite difficult things in maths have been re-discovered independently by mathematicians - doesn't mean the results are easy

Jonas Teuwen

8:24 PM

Mm.

skullpatrol

@OldJohn Re-discovery is not an embarrassment, correct?

Old John

@skullpatrol correct

Jonas Teuwen

Life is way too long for patience and virtue.

skullpatrol

@OldJohn Especially if it is done by very different methods.

Old John

@skullpatrol Indeed

Ethan

8:35 PM

hey

skullpatrol

hi

Ethan

how do I see math tex in this chat?]

what do I enable

$a$

Johan Larsson

Is Tron st the best album ever? Found it a couple of hours ago so early to say, but looks promising.

skullpatrol

@Ethan Do you have ChatJax?

Ethan

no

skullpatrol

8:39 PM

@Ethan Click on the top message "LATEX support for chat" on the right panel.

Ethan

where is that

I dont see it

skullpatrol

52

A: Should chat have TeX support?

This bookmark processes the current page with MathJax. It has been modified from the bookmark on this page to handle $$...$$ and to handle \\[...\\] properly, to include AMS additions, and to update automatically. The COPY TO CLIPBOARD link on pastebin.com should copy the bookmark to your clipbo...

@Ethan see it^ now?

Ethan

$a$

sec

skullpatrol

@JohanLarsson Is that from the movie "Tron"?

Ethan

I got it working thanks

lol

skullpatrol

8:45 PM

np

Johan Larsson

@skullpatrol yep, Daft Punk + 85 pcs. orchestra, think it is London philharmonic.

skullpatrol

@JohanLarsson Sounds pretty cool.

Johan Larsson

I have had goosebumps the past ten hours :)

Jonas Teuwen

8:59 PM

Maybe you should turn up the heating.

Johan Larsson

or turn up the volume?

skullpatrol

9:30 PM

Johan Larsson

@skullpatrol yeah!

hhh

9:49 PM

I thought Fermi-Dirac and Bose-Einstein statistic are Gaussian functions but they are not?!What is the mathematical form of this equation?

(Maxwell Boltzman's PDF is Gaussian but what is this?)

Just exponential or some specific term?

...wondering what is the fourier-transform of this with respect to xyz coordinates?

Moved here.

anon

@hhh, you realize the expression you have in chat and in that question are slightly different (namely, whether the -1 is in the exponent or not)

also, where are x,y,z variables in that expression?

Old John

10:06 PM

Ho ho ho @JasperLoy

user19161

@OldJohn Ho ho ho.

user19161

I uninstalled Flash and am trying not to use it to see if I can go without it.

Old John

@JasperLoy I have managed without flash for a week or two on my desktop - just haven't bothered to update it :)

user19161

@OldJohn I really dislike using Mint.

user19161

I think Mint is not as polished as Ubuntu, and Ubuntu is not as polished as Debian.

Old John

10:10 PM

@JasperLoy I have been quite pleased with it - but would prefer to go back to Slackware

user19161

Also, Ubuntu GNOME remix is not as polished as Ubuntu.

user19161

Also, apt is better than yum or zypper or urpmi.

user19161

Overall, I think that after Debian the best distro is ...

Old John

slackware!

user19161

... Mageia!

user19161

10:12 PM

In fact, Mageia and Debian have several similarities.

user19161

Both are independent and not backed by a company.

user19161

apt and urpmi both have global removal of orphaned dependencies.

Old John

I see Zev is back ... and in good form

user19161

Both are rather polished and stable.

user19161

Both need some workabout to install wireless firmware!

user19161

10:15 PM

And finally, both default to blue! HAHAHAHAHAHAHA.

hhh

10:26 PM

@anon Thanks it was a bug, fixed.

user19161

Only cockroaches are bugs.

Ethan

anon

hhh

@anon It is a good question, I don't know yet how to convert the energies and degenecrazy into $\bar x$ -- or perhaps I could integrate with respect to something else -- think how to get frequencies out of it.

user19161

10:43 PM

@Ethan Hey!

Ethan

hi

user19161

I have voted on exactly 999 questions and 999 answers, miracle!

user19161

@Ethan Have you talked to any prof yet?

Ethan

no

not yet

lol

user19161

@Ethan You can even try to apply to UCLA for your undergrad!

Ethan

10:46 PM

how does that work?

user19161

@Ethan Just a thought, you showing your work and applying there are two different things.

user19161

But the math courses there seem pretty good.

user19161

Wow, I have 5+5=10 stars on the wall!

Potato

Any analysts around, particularly those of the complex kind?

Ed Gorcenski

11:01 PM

sigh

Remember kids, copy-pasta code is your enemy

Ethan

what u need potato

user19161

@EdGorcenski Why?

Ethan

11:18 PM

hello

user19161

@Ethan Hello, LOL.

Potato

I need an answer to my bounty!

Ethan

11:40 PM

can i get a link

nvm

I dont understand iyt

it*

lol

Potato

10

Q: Zeros of a holomorphic function

Suppose $\Omega$ is a bounded domain in the plane whose boundary consist of $m+1$ disjoint analytic simple closed curves. Let $f$ be holomorphic and nonconstant on a neighborhood of the closure of $\Omega$ such that $$|f(z)|=1$$ for all $z$ in the boundary of $\Omega$. If $m=0$, then the maxim...